/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.xml.bind;

import org.w3c.dom.Node;

import java.util.Collections;
import java.util.Map;
import java.util.Properties;
import java.io.IOException;
import java.io.InputStream;

/**
 * <p> The <tt>JAXBContext</tt> class provides the client's entry point to the JAXB API. It provides
 * an abstraction for managing the XML/Java binding information necessary to implement the JAXB
 * binding framework operations: unmarshal, marshal and validate.
 *
 * <p>A client application normally obtains new instances of this class using one of these two
 * styles for newInstance methods, although there are other specialized forms of the method
 * available:
 *
 * <ul> <li>{@link #newInstance(String, ClassLoader) JAXBContext.newInstance(
 * "com.acme.foo:com.acme.bar" )} <br/> The JAXBContext instance is initialized from a list of colon
 * separated Java package names. Each java package contains JAXB mapped classes, schema-derived
 * classes and/or user annotated classes. Additionally, the java package may contain JAXB package
 * annotations that must be processed. (see JLS, Section 7.4.1 "Named Packages"). </li> <li>{@link
 * #newInstance(Class...) JAXBContext.newInstance( com.acme.foo.Foo.class )} <br/> The JAXBContext
 * instance is initialized with class(es) passed as parameter(s) and classes that are statically
 * reachable from these class(es). See {@link #newInstance(Class...)} for details. </li> </ul>
 *
 * <p> <i><B>SPEC REQUIREMENT:</B> the provider must supply an implementation class containing the
 * following method signatures:</i>
 *
 * <pre>
 * public static JAXBContext createContext( String contextPath, ClassLoader classLoader,
 * Map&lt;String,Object> properties ) throws JAXBException
 * public static JAXBContext createContext( Class[] classes, Map&lt;String,Object> properties )
 * throws JAXBException
 * </pre>
 *
 * <p><i> The following JAXB 1.0 requirement is only required for schema to java
 * interface/implementation binding. It does not apply to JAXB annotated classes. JAXB Providers
 * must generate a <tt>jaxb.properties</tt> file in each package containing schema derived classes.
 * The property file must contain a property named <tt>javax.xml.bind.context.factory</tt> whose
 * value is the name of the class that implements the <tt>createContext</tt> APIs.</i>
 *
 * <p><i> The class supplied by the provider does not have to be assignable to
 * <tt>javax.xml.bind.JAXBContext</tt>, it simply has to provide a class that implements the
 * <tt>createContext</tt> APIs.</i>
 *
 * <p><i> In addition, the provider must call the {@link DatatypeConverter#setDatatypeConverter(DatatypeConverterInterface)
 * DatatypeConverter.setDatatypeConverter} api prior to any client invocations of the marshal and
 * unmarshal methods.  This is necessary to configure the datatype converter that will be used
 * during these operations.</i>
 *
 * <a name="Unmarshalling"></a> <h3>Unmarshalling</h3> <p> The {@link Unmarshaller} class provides
 * the client application the ability to convert XML data into a tree of Java content objects. The
 * unmarshal method allows for any global XML element declared in the schema to be unmarshalled as
 * the root of an instance document. Additionally, the unmarshal method allows for an unrecognized
 * root element that has  an xsi:type attribute's value that references a type definition declared
 * in the schema  to be unmarshalled as the root of an instance document. The <tt>JAXBContext</tt>
 * object allows the merging of global elements and type definitions across a set of schemas (listed
 * in the <tt>contextPath</tt>). Since each schema in the schema set can belong to distinct
 * namespaces, the unification of schemas to an unmarshalling context should be namespace
 * independent.  This means that a client application is able to unmarshal XML documents that are
 * instances of any of the schemas listed in the <tt>contextPath</tt>.  For example:
 *
 * <pre>
 *        JAXBContext jc = JAXBContext.newInstance( "com.acme.foo:com.acme.bar" );
 *        Unmarshaller u = jc.createUnmarshaller();
 *        FooObject fooObj = (FooObject)u.unmarshal( new File( "foo.xml" ) ); // ok
 *        BarObject barObj = (BarObject)u.unmarshal( new File( "bar.xml" ) ); // ok
 *        BazObject bazObj = (BazObject)u.unmarshal( new File( "baz.xml" ) ); // error,
 * "com.acme.baz" not in contextPath
 * </pre>
 *
 * <p> The client application may also generate Java content trees explicitly rather than
 * unmarshalling existing XML data.  For all JAXB-annotated value classes, an application can create
 * content using constructors. For schema-derived interface/implementation classes and for the
 * creation of elements that are not bound to a JAXB-annotated class, an application needs to have
 * access and knowledge about each of the schema derived <tt> ObjectFactory</tt> classes that exist
 * in each of java packages contained in the <tt>contextPath</tt>.  For each schema derived java
 * class, there is a static factory method that produces objects of that type.  For example, assume
 * that after compiling a schema, you have a package <tt>com.acme.foo</tt> that contains a schema
 * derived interface named <tt>PurchaseOrder</tt>.  In order to create objects of that type, the
 * client application would use the factory method like this:
 *
 * <pre>
 *       com.acme.foo.PurchaseOrder po =
 *           com.acme.foo.ObjectFactory.createPurchaseOrder();
 * </pre>
 *
 * <p> Once the client application has an instance of the the schema derived object, it can use the
 * mutator methods to set content on it.
 *
 * <p> For more information on the generated <tt>ObjectFactory</tt> classes, see Section 4.2 <i>Java
 * Package</i> of the specification.
 *
 * <p> <i><B>SPEC REQUIREMENT:</B> the provider must generate a class in each package that contains
 * all of the necessary object factory methods for that package named ObjectFactory as well as the
 * static <tt>newInstance( javaContentInterface )</tt> method</i>
 *
 * <h3>Marshalling</h3> <p> The {@link Marshaller} class provides the client application the ability
 * to convert a Java content tree back into XML data.  There is no difference between marshalling a
 * content tree that is created manually using the factory methods and marshalling a content tree
 * that is the result an <tt>unmarshal </tt> operation.  Clients can marshal a java content tree
 * back to XML data to a <tt>java.io.OutputStream</tt> or a <tt>java.io.Writer</tt>.  The
 * marshalling process can alternatively produce SAX2 event streams to a registered
 * <tt>ContentHandler</tt> or produce a DOM Node object. Client applications have control over the
 * output encoding as well as whether or not to marshal the XML data as a complete document or as a
 * fragment.
 *
 * <p> Here is a simple example that unmarshals an XML document and then marshals it back out:
 *
 * <pre>
 *        JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
 *
 *        // unmarshal from foo.xml
 *        Unmarshaller u = jc.createUnmarshaller();
 *        FooObject fooObj = (FooObject)u.unmarshal( new File( "foo.xml" ) );
 *
 *        // marshal to System.out
 *        Marshaller m = jc.createMarshaller();
 *        m.marshal( fooObj, System.out );
 * </pre>
 *
 *
 * <h3>Validation</h3> <p> Validation has been changed significantly since JAXB 1.0.  The {@link
 * Validator} class has been deprecated and made optional.  This means that you are advised not to
 * use this class and, in fact, it may not even be available depending on your JAXB provider.  JAXB
 * 1.0 client applications that rely on <tt>Validator</tt> will still work properly when deployed
 * with the JAXB 1.0 runtime system.
 *
 * In JAXB 2.0, the {@link Unmarshaller} has included convenince methods that expose the JAXP 1.3
 * {@link javax.xml.validation} framework.  Please refer to the {@link
 * Unmarshaller#setSchema(javax.xml.validation.Schema)} API for more information.
 *
 *
 * <h3>JAXB Runtime Binding Framework Compatibility</h3> <p> The following JAXB 1.0 restriction only
 * applies to binding schema to interfaces/implementation classes. Since this binding does not
 * require a common runtime system, a JAXB client application must not attempt to mix runtime
 * objects (<tt>JAXBContext, Marshaller</tt>, etc. ) from different providers.  This does not mean
 * that the client application isn't portable, it simply means that a client has to use a runtime
 * system provided by the same provider that was used to compile the schema.
 *
 *
 * <h3>Discovery of JAXB implementation</h3> <p> When one of the <tt>newInstance</tt> methods is
 * called, a JAXB implementation is discovered by the following steps.
 *
 * <ol> <li> For each package/class explicitly passed in to the {@link #newInstance} method, in the
 * order they are specified, <tt>jaxb.properties</tt> file is looked up in its package, by using the
 * associated classloader &mdash; this is {@link Class#getClassLoader() the owner class loader} for
 * a {@link Class} argument, and for a package the specified {@link ClassLoader}.
 *
 * <p> If such a file is discovered, it is {@link Properties#load(InputStream) loaded} as a property
 * file, and the value of the {@link #JAXB_CONTEXT_FACTORY} key will be assumed to be the provider
 * factory class. This class is then loaded by the associated classloader discussed above.
 *
 * <p> This phase of the look up allows some packages to force the use of a certain JAXB
 * implementation. (For example, perhaps the schema compiler has generated some vendor extension in
 * the code.)
 *
 * <li> If the system property {@link #JAXB_CONTEXT_FACTORY} exists, then its value is assumed to be
 * the provider factory class. This phase of the look up enables per-JVM override of the JAXB
 * implementation.
 *
 * <li> Look for <tt>/META-INF/services/javax.xml.bind.JAXBContext</tt> file in the associated
 * classloader. This file follows the standard service descriptor convention, and if such a file
 * exists, its content is assumed to be the provider factory class. This phase of the look up is for
 * automatic discovery. It allows users to just put a JAXB implementation in a classpath and use it
 * without any furhter configuration.
 *
 * <li> Finally, if all the steps above fail, then the rest of the look up is unspecified. That
 * said, the recommended behavior is to simply look for some hard-coded platform default JAXB
 * implementation. This phase of the look up is so that JavaSE can have its own JAXB implementation
 * as the last resort. </ol>
 *
 * <p> Once the provider factory class is discovered, its <tt>public static JAXBContext
 * createContext(String,ClassLoader,Map)</tt> method (see {@link #newInstance(String, ClassLoader,
 * Map)} for the parameter semantics.) or <tt>public static JAXBContext
 * createContet(Class[],Map)</tt> method (see {@link #newInstance(Class[], Map)} for the parameter
 * semantics) are invoked to create a {@link JAXBContext}.
 *
 * @author <ul><li>Ryan Shoemaker, Sun Microsystems, Inc.</li><li>Kohsuke Kawaguchi, Sun
 *         Microsystems, Inc.</li><li>Joe Fialli, Sun Microsystems, Inc.</li></ul>
 * @see Marshaller
 * @see Unmarshaller
 * @see S 7.4.1 "Named Packages" in Java Language Specification</a>
 * @since JAXB1.0
 */
public abstract class JAXBContext {

  /**
   * The name of the property that contains the name of the class capable
   * of creating new <tt>JAXBContext</tt> objects.
   */
  public static final String JAXB_CONTEXT_FACTORY =
      "javax.xml.bind.context.factory";


  protected JAXBContext() {
  }


  /**
   * <p>
   * Obtain a new instance of a <tt>JAXBContext</tt> class.
   *
   * <p>
   * This is a convenience method to invoke the
   * {@link #newInstance(String, ClassLoader)} method with
   * the context class loader of the current thread.
   *
   * @throws JAXBException if an error was encountered while creating the <tt>JAXBContext</tt> such
   * as <ol> <li>failure to locate either ObjectFactory.class or jaxb.index in the packages</li>
   * <li>an ambiguity among global elements contained in the contextPath</li> <li>failure to locate
   * a value for the context factory provider property</li> <li>mixing schema derived packages from
   * different providers on the same contextPath</li> </ol>
   */
  public static JAXBContext newInstance(String contextPath)
      throws JAXBException {

    //return newInstance( contextPath, JAXBContext.class.getClassLoader() );
    return newInstance(contextPath, getContextClassLoader());
  }

  /**
   * <p>
   * Obtain a new instance of a <tt>JAXBContext</tt> class.
   *
   * <p>
   * The client application must supply a context path which is a list of
   * colon (':', \u005Cu003A) separated java package names that contain
   * schema-derived classes and/or fully qualified JAXB-annotated classes.
   * Schema-derived
   * code is registered with the JAXBContext by the
   * ObjectFactory.class generated per package.
   * Alternatively than being listed in the context path, programmer
   * annotated JAXB mapped classes can be listed in a
   * <tt>jaxb.index</tt> resource file, format described below.
   * Note that a java package can contain both schema-derived classes and
   * user annotated JAXB classes. Additionally, the java package may
   * contain JAXB package annotations  that must be processed. (see JLS,
   * Section 7.4.1 "Named Packages").
   * </p>
   *
   * <p>
   * Every package listed on the contextPath must meet <b>one or both</b> of the
   * following conditions otherwise a <tt>JAXBException</tt> will be thrown:
   * </p>
   * <ol>
   * <li>it must contain ObjectFactory.class</li>
   * <li>it must contain jaxb.index</li>
   * </ol>
   *
   * <p>
   * <b>Format for jaxb.index</b>
   * <p>
   * The file contains a newline-separated list of class names.
   * Space and tab characters, as well as blank
   * lines, are ignored. The comment character
   * is '#' (0x23); on each line all characters following the first comment
   * character are ignored. The file must be encoded in UTF-8. Classes that
   * are reachable, as defined in {@link #newInstance(Class...)}, from the
   * listed classes are also registered with JAXBContext.
   * <p>
   * Constraints on class name occuring in a <tt>jaxb.index</tt> file are:
   * <ul>
   * <li>Must not end with ".class".</li>
   * <li>Class names are resolved relative to package containing
   * <tt>jaxb.index</tt> file. Only classes occuring directly in package
   * containing <tt>jaxb.index</tt> file are allowed.</li>
   * <li>Fully qualified class names are not allowed.
   * A qualified class name,relative to current package,
   * is only allowed to specify a nested or inner class.</li>
   * </ul>
   *
   * <p>
   * To maintain compatibility with JAXB 1.0 schema to java
   * interface/implementation binding, enabled by schema customization
   * <tt>&lt;jaxb:globalBindings valueClass="false"></tt>,
   * the JAXB provider will ensure that each package on the context path
   * has a <tt>jaxb.properties</tt> file which contains a value for the
   * <tt>javax.xml.bind.context.factory</tt> property and that all values
   * resolve to the same provider.  This requirement does not apply to
   * JAXB annotated classes.
   *
   * <p>
   * If there are any global XML element name collisions across the various
   * packages listed on the <tt>contextPath</tt>, a <tt>JAXBException</tt>
   * will be thrown.
   *
   * <p>
   * Mixing generated interface/impl bindings from multiple JAXB Providers
   * in the same context path may result in a <tt>JAXBException</tt>
   * being thrown.
   *
   * <p>
   * The steps involved in discovering the JAXB implementation is discussed in the class javadoc.
   *
   * @param contextPath list of java package names that contain schema derived class and/or java to
   * schema (JAXB-annotated) mapped classes
   * @param classLoader This class loader will be used to locate the implementation classes.
   * @return a new instance of a <tt>JAXBContext</tt>
   * @throws JAXBException if an error was encountered while creating the <tt>JAXBContext</tt> such
   * as <ol> <li>failure to locate either ObjectFactory.class or jaxb.index in the packages</li>
   * <li>an ambiguity among global elements contained in the contextPath</li> <li>failure to locate
   * a value for the context factory provider property</li> <li>mixing schema derived packages from
   * different providers on the same contextPath</li> </ol>
   */
  public static JAXBContext newInstance(String contextPath, ClassLoader classLoader)
      throws JAXBException {

    return newInstance(contextPath, classLoader, Collections.<String, Object>emptyMap());
  }

  /**
   * <p>
   * Obtain a new instance of a <tt>JAXBContext</tt> class.
   *
   * <p>
   * This is mostly the same as {@link JAXBContext#newInstance(String, ClassLoader)},
   * but this version allows you to pass in provider-specific properties to configure
   * the instantiation of {@link JAXBContext}.
   *
   * <p>
   * The interpretation of properties is up to implementations. Implementations should
   * throw <tt>JAXBException</tt> if it finds properties that it doesn't understand.
   *
   * @param contextPath list of java package names that contain schema derived classes
   * @param classLoader This class loader will be used to locate the implementation classes.
   * @param properties provider-specific properties. Can be null, which means the same thing as
   * passing in an empty map.
   * @return a new instance of a <tt>JAXBContext</tt>
   * @throws JAXBException if an error was encountered while creating the <tt>JAXBContext</tt> such
   * as <ol> <li>failure to locate either ObjectFactory.class or jaxb.index in the packages</li>
   * <li>an ambiguity among global elements contained in the contextPath</li> <li>failure to locate
   * a value for the context factory provider property</li> <li>mixing schema derived packages from
   * different providers on the same contextPath</li> </ol>
   * @since JAXB2.0
   */
  public static JAXBContext newInstance(String contextPath, ClassLoader classLoader,
      Map<String, ?> properties)
      throws JAXBException {

    return ContextFinder.find(
                        /* The default property name according to the JAXB spec */
        JAXB_CONTEXT_FACTORY,

                        /* the context path supplied by the client app */
        contextPath,

                        /* class loader to be used */
        classLoader,
        properties);
  }

// TODO: resurrect this once we introduce external annotations
//    /**
//     * <p>
//     * Obtain a new instance of a <tt>JAXBContext</tt> class.
//     *
//     * <p>
//     * The client application must supply a list of classes that the new
//     * context object needs to recognize.
//     *
//     * Not only the new context will recognize all the classes specified,
//     * but it will also recognize any classes that are directly/indirectly
//     * referenced statically from the specified classes.
//     *
//     * For example, in the following Java code, if you do
//     * <tt>newInstance(Foo.class)</tt>, the newly created {@link JAXBContext}
//     * will recognize both <tt>Foo</tt> and <tt>Bar</tt>, but not <tt>Zot</tt>:
//     * <pre>
//     * class Foo {
//     *      Bar b;
//     * }
//     * class Bar { int x; }
//     * class Zot extends Bar { int y; }
//     * </pre>
//     *
//     * Therefore, a typical client application only needs to specify the
//     * top-level classes, but it needs to be careful.
//     *
//     * TODO: if we are to define other mechanisms, refer to them.
//     *
//     * @param externalBindings
//     *      list of external binding files. Can be null or empty if none is used.
//     *      when specified, those files determine how the classes are bound.
//     *
//     * @param classesToBeBound
//     *      list of java classes to be recognized by the new {@link JAXBContext}.
//     *      Can be empty, in which case a {@link JAXBContext} that only knows about
//     *      spec-defined classes will be returned.
//     *
//     * @return
//     *      A new instance of a <tt>JAXBContext</tt>. Always non-null valid object.
//     *
//     * @throws JAXBException
//     *      if an error was encountered while creating the
//     *      <tt>JAXBContext</tt>, such as (but not limited to):
//     * <ol>
//     *  <li>No JAXB implementation was discovered
//     *  <li>Classes use JAXB annotations incorrectly
//     *  <li>Classes have colliding annotations (i.e., two classes with the same type name)
//     *  <li>Specified external bindings are incorrect
//     *  <li>The JAXB implementation was unable to locate
//     *      provider-specific out-of-band information (such as additional
//     *      files generated at the development time.)
//     * </ol>
//     *
//     * @throws IllegalArgumentException
//     *      if the parameter contains {@code null} (i.e., {@code newInstance(null);})
//     *
//     * @since JAXB2.0
//     */
//    public static JAXBContext newInstance( Source[] externalBindings, Class... classesToBeBound )
//        throws JAXBException {
//
//        // empty class list is not an error, because the context will still include
//        // spec-specified classes like String and Integer.
//        // if(classesToBeBound.length==0)
//        //    throw new IllegalArgumentException();
//
//        // but it is an error to have nulls in it.
//        for( int i=classesToBeBound.length-1; i>=0; i-- )
//            if(classesToBeBound[i]==null)
//                throw new IllegalArgumentException();
//
//        return ContextFinder.find(externalBindings,classesToBeBound);
//    }

  /**
   * <p>
   * Obtain a new instance of a <tt>JAXBContext</tt> class.
   *
   * <p>
   * The client application must supply a list of classes that the new
   * context object needs to recognize.
   *
   * Not only the new context will recognize all the classes specified,
   * but it will also recognize any classes that are directly/indirectly
   * referenced statically from the specified classes. Subclasses of
   * referenced classes nor <tt>&#64;XmlTransient</tt> referenced classes
   * are not registered with JAXBContext.
   *
   * For example, in the following Java code, if you do
   * <tt>newInstance(Foo.class)</tt>, the newly created {@link JAXBContext}
   * will recognize both <tt>Foo</tt> and <tt>Bar</tt>, but not <tt>Zot</tt> or <tt>FooBar</tt>:
   * <pre>
   * class Foo {
   *      &#64;XmlTransient FooBar c;
   *      Bar b;
   * }
   * class Bar { int x; }
   * class Zot extends Bar { int y; }
   * class FooBar { }
   * </pre>
   *
   * Therefore, a typical client application only needs to specify the
   * top-level classes, but it needs to be careful.
   *
   * <p>
   * Note that for each java package registered with JAXBContext,
   * when the optional package annotations exist, they must be processed.
   * (see JLS, Section 7.4.1 "Named Packages").
   *
   * <p>
   * The steps involved in discovering the JAXB implementation is discussed in the class javadoc.
   *
   * @param classesToBeBound list of java classes to be recognized by the new {@link JAXBContext}.
   * Can be empty, in which case a {@link JAXBContext} that only knows about spec-defined classes
   * will be returned.
   * @return A new instance of a <tt>JAXBContext</tt>. Always non-null valid object.
   * @throws JAXBException if an error was encountered while creating the <tt>JAXBContext</tt>, such
   * as (but not limited to): <ol> <li>No JAXB implementation was discovered <li>Classes use JAXB
   * annotations incorrectly <li>Classes have colliding annotations (i.e., two classes with the same
   * type name) <li>The JAXB implementation was unable to locate provider-specific out-of-band
   * information (such as additional files generated at the development time.) </ol>
   * @throws IllegalArgumentException if the parameter contains {@code null} (i.e., {@code
   * newInstance(null);})
   * @since JAXB2.0
   */
  public static JAXBContext newInstance(Class... classesToBeBound)
      throws JAXBException {

    return newInstance(classesToBeBound, Collections.<String, Object>emptyMap());
  }

  /**
   * <p>
   * Obtain a new instance of a <tt>JAXBContext</tt> class.
   *
   * <p>
   * An overloading of {@link JAXBContext#newInstance(Class...)}
   * to configure 'properties' for this instantiation of {@link JAXBContext}.
   *
   * <p>
   * The interpretation of properties is up to implementations. Implementations should
   * throw <tt>JAXBException</tt> if it finds properties that it doesn't understand.
   *
   * @param classesToBeBound list of java classes to be recognized by the new {@link JAXBContext}.
   * Can be empty, in which case a {@link JAXBContext} that only knows about spec-defined classes
   * will be returned.
   * @param properties provider-specific properties. Can be null, which means the same thing as
   * passing in an empty map.
   * @return A new instance of a <tt>JAXBContext</tt>. Always non-null valid object.
   * @throws JAXBException if an error was encountered while creating the <tt>JAXBContext</tt>, such
   * as (but not limited to): <ol> <li>No JAXB implementation was discovered <li>Classes use JAXB
   * annotations incorrectly <li>Classes have colliding annotations (i.e., two classes with the same
   * type name) <li>The JAXB implementation was unable to locate provider-specific out-of-band
   * information (such as additional files generated at the development time.) </ol>
   * @throws IllegalArgumentException if the parameter contains {@code null} (i.e., {@code
   * newInstance(null,someMap);})
   * @since JAXB2.0
   */
  public static JAXBContext newInstance(Class[] classesToBeBound, Map<String, ?> properties)
      throws JAXBException {

    if (classesToBeBound == null) {
      throw new IllegalArgumentException();
    }

    // but it is an error to have nulls in it.
    for (int i = classesToBeBound.length - 1; i >= 0; i--) {
      if (classesToBeBound[i] == null) {
        throw new IllegalArgumentException();
      }
    }

    return ContextFinder.find(classesToBeBound, properties);
  }

  /**
   * Create an <tt>Unmarshaller</tt> object that can be used to convert XML
   * data into a java content tree.
   *
   * @return an <tt>Unmarshaller</tt> object
   * @throws JAXBException if an error was encountered while creating the <tt>Unmarshaller</tt>
   * object
   */
  public abstract Unmarshaller createUnmarshaller() throws JAXBException;


  /**
   * Create a <tt>Marshaller</tt> object that can be used to convert a
   * java content tree into XML data.
   *
   * @return a <tt>Marshaller</tt> object
   * @throws JAXBException if an error was encountered while creating the <tt>Marshaller</tt>
   * object
   */
  public abstract Marshaller createMarshaller() throws JAXBException;


  /**
   * {@link Validator} has been made optional and deprecated in JAXB 2.0.  Please
   * refer to the javadoc for {@link Validator} for more detail.
   * <p>
   * Create a <tt>Validator</tt> object that can be used to validate a
   * java content tree against its source schema.
   *
   * @return a <tt>Validator</tt> object
   * @throws JAXBException if an error was encountered while creating the <tt>Validator</tt> object
   * @deprecated since JAXB2.0
   */
  public abstract Validator createValidator() throws JAXBException;

  /**
   * Creates a <tt>Binder</tt> object that can be used for
   * associative/in-place unmarshalling/marshalling.
   *
   * @param domType select the DOM API to use by passing in its DOM Node class.
   * @return always a new valid <tt>Binder</tt> object.
   * @throws UnsupportedOperationException if DOM API corresponding to <tt>domType</tt> is not
   * supported by the implementation.
   * @since JAXB2.0
   */
  public <T> Binder<T> createBinder(Class<T> domType) {
    // to make JAXB 1.0 implementations work, this method must not be
    // abstract
    throw new UnsupportedOperationException();
  }

  /**
   * Creates a <tt>Binder</tt> for W3C DOM.
   *
   * @return always a new valid <tt>Binder</tt> object.
   * @since JAXB2.0
   */
  public Binder<Node> createBinder() {
    return createBinder(Node.class);
  }

  /**
   * Creates a <tt>JAXBIntrospector</tt> object that can be used to
   * introspect JAXB objects.
   *
   * @return always return a non-null valid <tt>JAXBIntrospector</tt> object.
   * @throws UnsupportedOperationException Calling this method on JAXB 1.0 implementations will
   * throw an UnsupportedOperationException.
   * @since JAXB2.0
   */
  public JAXBIntrospector createJAXBIntrospector() {
    // to make JAXB 1.0 implementations work, this method must not be
    // abstract
    throw new UnsupportedOperationException();
  }

  /**
   * Generates the schema documents for this context.
   *
   * @param outputResolver this object controls the output to which schemas will be sent.
   * @throws IOException if {@link SchemaOutputResolver} throws an {@link IOException}.
   * @throws UnsupportedOperationException Calling this method on JAXB 1.0 implementations will
   * throw an UnsupportedOperationException.
   * @since JAXB 2.0
   */
  public void generateSchema(SchemaOutputResolver outputResolver) throws IOException {
    // to make JAXB 1.0 implementations work, this method must not be
    // abstract
    throw new UnsupportedOperationException();
  }

  private static ClassLoader getContextClassLoader() {
    if (System.getSecurityManager() == null) {
      return Thread.currentThread().getContextClassLoader();
    } else {
      return (ClassLoader) java.security.AccessController.doPrivileged(
          new java.security.PrivilegedAction() {
            public java.lang.Object run() {
              return Thread.currentThread().getContextClassLoader();
            }
          });
    }
  }

}
